The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

+ References

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of options outstanding, including both vested and non-vested options.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(ii)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

+ References

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The floor of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

+ Details

Name:	us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLowerRangeLimit
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

The ceiling of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

+ References

+ Details

Name:	us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 718
-SubTopic 10
-Subparagraph (e)(1)
-Name Accounting Standards Codification
-Paragraph 2
-Section 50
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

+ Details

Name:	us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis=jec_RangeOfExercisePricesFrom031.38Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis=jec_RangeOfExercisePricesFrom31.38To39.05Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Employee Stock Purchase and Stock Incentive Plans - Schedule Of Information Regarding Outstanding Options (Details) - $ / shares	12 Months Ended
	Sep. 27, 2024	Sep. 29, 2023	Sep. 30, 2022	Oct. 01, 2021
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Range of exercise prices for options outstanding, minimum (in dollars per share)	$ 9.55	$ 5.64	$ 5.64
Range of exercise prices for options outstanding, maximum (in dollars per share)	$ 36.73	$ 60.43	$ 60.43
Options Outstanding, Number (in shares)	90,796	217,481	439,349	573,984
Options Exercisable, Number (in shares)	90,796
Options Outstanding, Weighted Average Remaining Contractual Life (years)	4 years 4 months 17 days
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 19.03
Options Outstanding, Weighted Average Price (in dollars per share)	19.03	$ 31.43	$ 35.77	$ 45.65
$0.00 - $31.38
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Range of exercise prices for options outstanding, minimum (in dollars per share)	0.00
Range of exercise prices for options outstanding, maximum (in dollars per share)	$ 31.38
Options Outstanding, Number (in shares)	61,870
Options Exercisable, Number (in shares)	61,870
Options Outstanding, Weighted Average Remaining Contractual Life (years)	6 years 3 days
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 11.13
Options Outstanding, Weighted Average Price (in dollars per share)	11.13
$31.38 - $39.05
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Range of exercise prices for options outstanding, minimum (in dollars per share)	31.38
Range of exercise prices for options outstanding, maximum (in dollars per share)	$ 39.05
Options Outstanding, Number (in shares)	28,926
Options Exercisable, Number (in shares)	28,926
Options Outstanding, Weighted Average Remaining Contractual Life (years)	10 months 24 days
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 35.93
Options Outstanding, Weighted Average Price (in dollars per share)	$ 35.93